The invention relates to vacuum packaging of materials, and methods for accomplishing such packaging. Specifically, the invention relates to the vacuum packaging of materials in semi-rigid or non-rigid packaging which can be heat sealed.
Vacuum packaging is useful for the isolation of a material from the environment for definite or indefinite periods of time. This isolation may be desirable because the packaged material is sensitive to environmental conditions, or because the material is to be used in a process which must be isolated from the environment.
For example, some of the useful applications for vacuum packaging are for foodstuffs, medical materials, pharmaceutical applications, electronic components, and a wide variety of air-, oxygen-, or moisture-sensitive materials.
There are packaging applications in which it is desirable to be able to draw a vacuum on the contents of a flexible bag and then seal the bag against the introduction of air. A convenient method of sealing such bags is by heat sealing. One such application is in home food packaging, for example. Several systems are commercially available which allow the individual to draw the air out of a bag and then provide a seal against further air intrusion. For example, U.S. Pat. No. RE 34,929 to Kristen, and U.S. Pat. No. 4,941,310 to Kristen are representative. In these systems, the manufacturer""s packaging material must be used, since that material is specially configured to allow air to flow to the vacuum pump inlet inside the bag while the atmospheric pressure on the outside of the bag squeezes the top and bottom panels of the bag tightly together. In order to provide this flow passage, the bag material is corrugated, quilted, or otherwise provided with macroscopic channels. The panels of the plastic film must be stiff enough to support the xe2x80x9cvacuum flowxe2x80x9d channels against the external loads.
One successful consumer-use vacuum packaging/heat sealing system is known as Foodsaver (Tilia Inc., San Francisco, USA). This system employs a bag with the inner face of one bag panel quilted into a diamond pattern. The pattern is self-supporting to the extent that a passage is always provided between the upper and lower faces to allow evacuation, even when the opposing panels are brought together by the forces of vacuum.
There are many potential applications for vacuum packaging for which no quilted materials are available. The success of the vacuum package depends on the ability to draw air from the packaged material, between smooth materials, and out across the location of the final seal. Unfortunately, panels of smooth film, when subjected to external pressure, press tightly against each other, effectively blocking further flow of trapped air toward the pump orifice.
Other prior art processes use a device known as a snorkel to place a vacuum source within an unsealed semi-rigid or non-rigid package, so that withdrawal of the atmosphere within the package can be accomplished with application of a vacuum to the snorkel. The panels of the bag tend not to collapse to the extent of preventing the escape of air when a snorkel is used. Complete sealing of the bag, by such means as heat sealing, is then carried out. The snorkel can be withdrawn from the bag essentially instantaneously with the sealing operation, but this method does not achieve as high a vacuum as is possible otherwise. The snorkel can also be left in the bag, to be retrieved after another seal is made between the trapped snorkel and the material in the bag. Some representative snorkel-type devices and methods have been described in U.S. Pat. No. 5,711,136 to Carcano, U.S. Pat. No. 5,551,213 to Koelsch et al., and U.S. Pat. No. 5,501,525 to Cox et al.
The invention results from a realization that semi-rigid or non-rigid packages which are to be evacuated is more efficiently evacuated when a duct of fusible material extends into an unsealed package, a vacuum drawn through the duct, and the package sealed without removing the duct. The duct can be sealed into the package and can partially or wholly form the seal of the package. Before sealing, the duct provides a passage for the withdrawal of atmosphere from the package, and the passage does not collapse upon the application of vacuum to the package. This can be a problem, particularly if the interior walls of the package are smooth. The duct can be made of material that prevents or greatly inhibits the undesired removal of substances in the package, such as can occur during the vacuum sealing of packages containing granular substances.
In general, the invention provides a method of evacuating a package. The method includes providing an unsealed semi-rigid or non-rigid package with a duct including fusible material. The package includes an upper panel and a lower panel, and between these is an interior region. The panels are heat sealable at their peripheries to form a fluid-tight barrier between the interior region and the external environment. The duct includes an internal end and an external end. The internal end is inserted into the interior region of the package, and the external end is in association with a vacuum source external to the package. The internal end of the duct can extend as far into the package as necessary to allow the vacuum source to effectively remove atmosphere from the package interior. The extent to which the duct must be inserted into the package may depend on the characteristics of the inner surfaces of the upper and lower panels, or the nature of any material within the package interior. The method also includes drawing a vacuum on the interior region of the package by applying vacuum to the external end of the duct; and the method includes heat sealing the unsealed portion of the periphery of the package, without removing the duct, to provide a fluid-tight barrier between the interior region of the package and the external environment. Optionally, the package can have a fluid tight seal around between about 50 and 99% of its periphery, or around between about 75 and 99% of its periphery. Further optionally, the package can be sealed around its periphery, except for the portion of the periphery overlapped by the duct.
The fusible material can be woven or non-woven fabric, open cell foam, paper, or fiber sheet. The interior region of the package can be at least partially filled with granular material. The package can be made from a material such as coated cellophane, cellulose acetate, coated polyester, poly (chlorotrifluoroethylene), polyethylene, polystyrene, polyvinyl alcohol, nonrigid polyvinyl chloride and copolymers thereof, polyvinyl chloride-nitrile rubber blend, polyvinylidene chloride, rubber hydrochloride, fluorinated ethylene-propylene copolymer, flexible vinyl, or SURLYN thermoplastic ionomer-lined multi-layer film.
In another aspect, the invention provides a vacuum packaging aid including a duct of fusible material having an internal end and an external end. The internal end extends into an interior region of an unsealed semi-rigid or non-rigid package, and the external end is in association with a vacuum source. The fusible material can be woven or non-woven fabric, open cell foam, paper, or fiber sheet.
In a further aspect, the invention provides a method of evacuating a package. The method includes providing an unsealed semi-rigid or non-rigid package with a duct. The package includes upper and lower panels, between which is an interior region. The panels are heat sealable to form a fluid-tight barrier between the interior region and the external environment. The duct includes an internal end and an external end, the internal end being inserted into the interior region of the package, and the external end being in association with a vacuum source external to the package. The method further includes drawing a vacuum on the interior region of the package by applying vacuum on the external end of the duct. The invention further includes sealing the package, so that the duct forms at least part of a fluid-tight barrier between the interior region of the package and the external environment.
As used in the claims, the term xe2x80x9cmacroscopic passagexe2x80x9d refers to a passage through a duct that does not require passage of gas through the walls of the duct, or the substance of the duct itself. Rather gas is evacuated through a void in the duct which is larger than any void which may exist in the material comprising the duct walls.
As used the in claims, the term xe2x80x9cgranular materialxe2x80x9d refers to a particulate substance with particles of size no larger than approximately 5 mm in diameter. The lower size limit of the particulate substance can be, but is not necessarily, limited by the material used as a fusible duct, or alternately the size of a macroscopic passage formed with the duct. Granular material can include highly pulverized material with very small diameters. The particles need not be of any particular shape, but can be spherical, roughly spherical, cubic, or non regular in shape.
As used in the claims, the term xe2x80x9cheat sealingxe2x80x9d refers to the bonding or welding of a material to itself or to another material by the use of heat. This can be done with or without the use of adhesive, depending on the nature of the materials.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.